Mainspring slipping ring for a self-winding timepiece

ABSTRACT

An overwind release terminal blade of a main spring in a barrel comprising one portion increasing in thickness and a second portion decreasing in thickness in the direction of the outer extremity of the terminal blade.

I :United States Patent Relerences Cited UNITED STATES PATENTS 3/1969 lwasawa et al.

(72] Inventor Jean lhueter Geneva, Switzerland 869,561

3,433,0ll 3,465,514 9/1969 Haueter............. 3,130,538 4/1964 Bourguin et al. 43,464 7/1864 Philippe FORElGN PATENTS 7/1863 GreatBritain Switurllld 161 1 1/68 Primary Examiner- Richard B. Wilkinson 4 Mmsmc SLmmc RING FOR A SELF Assistant Examiner-George H. Miller, Jr.

' WINDING TIMEPm Attorneys-Kenwood Ross and Chester E. Flavin 7 Claims, 4 Drawing Figs.

8/86 ABSTRACT: An overwind release terminal blade of a main v G04b 1/16 spring in a barrel comprising one portion increasing in thickness and a second portion 58/59, 80, decreasing in thickness in the 86, 87 direction of the outer extremity of the terminal blade.

PATENTED AUG] 7 I971 SHEET 1 UF 2 FIG. '7

INVENTOR.

Jean HAUETEH BY Kmwwd (VIM/L5 ATTORNEYS.

MAINSPRING SLIPPING RING FOR A SELF-WINDING TIMEPIECE spring is generally not secured to the barrel, as in the conven- 1 tional watches, but is connected to the barrel through the intermediary of a supplementary elastic blade, called slipping blade, made in such a way that it is applied elastically against the wall of the barrel. This slipping blade does not effect a relative movement with respect to the barrel so long the wind of the main spring is lower than a determined value. When this wind value of the main spring is reached, the slipping blade slips on the inner wall of the barrel, that prevents any overwind of the main spring even when the self-winding device continues to operate.

The slipping blade is secured to the extremity of the outer end of the main spring by rivets or, more generally, by points of electric welding. The assembling and the securing of the slipping blade to the main spring are difficult to be carried out, due to the fact that the longitudinal axis of the main spring and of the slipping blade must be in a very precise alignment. Moreover, the rivets or the welding can take play, that renders the watch unusable.

Moreover, these slipping blades bear generally only at three points on the wall of the barrel, so that, after wear and tear of the material and degradation of the lubricate, they show a tendency to seize on the barrel, that produces an overwind of the spring. 4

It has been suggested, so as to prevent these drawbacks, to make the slipping blade of one piece with the main spring, as an overthickness of the ending portion of the main spring.

Such slipping blades, provided'for bearing on their whole length on the wall of the barrel, show the reverse drawback as the blades made of two pieces with the main spring, in that, after wear and tear, they release too easily so that the main spring is then constantly uride'rwound.

The object of the present invention is to prevent these drawbacks.

The driving device according to the invention is characterized by the fact that the terminal blade of the main spring, made of one piece thereof, comprises at least two portions, one of which, called entrance portion, has, at its beginning, a thickness equal to the thickness of the blade of the main spring and which increases in the direction of the outer extremity of said blade, and the other portion of which, called output portion, has, at its beginning, a thickness equal to the greatest thickness of the end of the first portion and which decreases in the direction of the extremity of the said blade, the arrangement being such that the extremity of the output portion of the blade does not bear continuously on the inner face of the wall of the barrel but bears on this wall at two points situated at distance one from another, one of which being constituted by the proper extremity of this portion, the spring bearing on the part of this portion distant from the wall of the barrel for exerting thereon a pressure varying with its wind, the whole in such a way that, when the said wind increases, the said pressure decreases, thus permitting the said blade to rotate in the barrel when the wind of the main spring reaches a critical value, this rotation releasing the said wind so that the pressure exerted on the output portion of the blade increases anew, that makes anew the said blade rigid with the barrel.

The drawing shows, by way of example, one embodiment of the object of the invention.

FIG. 1 is a plan view of a barrel for timepiece provided with its main spring, in which have been represented diagrammatically the forces exerted by the main spring on the lateral wall of the barrel.

FIG. 2 is a plan view of a detail of FIG. 1, at an enlarged scale, and

FIGS. 3 and 4 are diagrams of two main springs, one (FIG. 3) being a conventional main spring with slipping blade made of two pieces, and the other one (FIG. 4) being according to the invention.

The lateral wall of the barrel represented is designated by I and the main spring by 2. Its outer end 20 is prolongated by a blade, made of one piece thereof, presenting three portions, one of which, called entrance portion, designated by 2b, extends on a sector a of about 10, measured at the center of the barrel, the second portion of which, called intermediary portion, designated by 20, extends on a sector B of about and the third portion of which, called output portion, designated by 2d, extends on a sector 7 of about The thickness of the entrance portion 2b of the terminal blade is increasing from its beginning, where it corresponds to the nominal thickness of the blade of the spring, up to its extremity where it is 1.7 time thicker. The thickness of the intermediary portion 2c is constant and corresponds to the maximum thickness of the entrance portion 2b, while the thickness of the output portion 2d is decreasing and corresponds, at its beginning, to the thickness of the intermediary portion 2c for going, at its free extremity, up to the nominal thickness of the blade of the spring. The free extremity of the output portion 2b is chamfered at 3.

The end of the output portion 2d, at the place indicated by 2e, does not bear on the lateral wall of the barrel 1 and bears on this wall only at two points distant one from another, one, situated at the chamfered extremity 3 of the blade and the other situated at 4. This portion 2e which is distant from the wall 1 of the barrel extends on a sector 6, of 70, measured'at the center of the barrel.

The outer blade 2a of the main spring bears, in the neighborhood of its extremity, on the portion 2e of the blade and exerts thereon a radial pressure, directed outwardly, which varies with the wind of the main spring.

This variation of the pressure exerted by the outer part 2a of the main spring on the portion 2e of the terminal blade is illustrated at FIG. 2 where the terminal blade is represented in full lines in the position that it occupies when the main spring is wound at the maximum, at the time which preceeds the moment where the blade releases, and where the outer part 2a is represented in dotted lines in the position that it occupies when the main spring is slightly unwound, immediately after each releasing of the blade.

FIG. 2 shows that, between these two positions, the outer blade 2a of the main spring effects a movement of pulsation during which it is radially moved, in the direction indicated by arrows 6 in FIG. 1 in which the main spring is represented in its intermediary position. Obviously these radial displacements of the portion 2a of the main spring modify the pressure that this terminal portion exerts on the portion 2e of the blade.

Moreover, the point of bearing of the terminal portion 2a on the portion 2e, designated by 7 in FIG. 2, is also displaced along the portion 2e, during the pulsating movement of the portion 20, as indicated by the arrow 8 of FIG. I.

There results that the radial forces exerted by the terminal portion of the main spring on the lateral wall 1 of the barrel, and which have been represented diagrammatically in FIG. 1, vary with the wind of the main spring. These forces are distributed in three distinct areas indicated by the curves 9, I0 and ll of FIG. 1: The area 10 extends on a sector, measured at the center of the barrel, of about I80 and comprises only relatively low forces; the area 9 extends on about 60 and comprises more important forces while the area 11, which extends only on some degrees, comprises very high forces due to the pressure exerted by the terminal portion 20 on the portion 2e of the blade, in the neighborhood of its extremity.

In these three areas, the hatched surface corresponds to the forces exerted on the wall I of the barrel immediately before the releasing of the blade, while the surfaces which are not hatched represent the forces immediately after this releasing.

The experience has shown that such a repartition of the forces, due to the shape as disclosed and represented of the terminal blade of the main spring, conduces to a main spring operating specially favorably, as illustrated in FIG. 4.

For better showing these advantages, the drawbacks of the conventional main spring, with slipping blade made of two pieces, will be indicated hereafter, while referring to the diagram of FIG. 3.

In this figure, the lower curve represents the moment of forces of the main spring with respect to its wind; M is the moment of the spring entirely wound, when it starts to unwind, while M, indicates the moment of forces of the main spring after 24 hours of running, each inclined graduation of the diagram representing a revolution of the barrel, that is to say 6 hours of running of the watch. The upper curve of the diagram indicates the slipping moment Mgl. of the slipping blade. The first portion of this curve, situated at the left of the vertical line designated by 12 in FIG. 3, indicates the slipping moment Mgl. for a slow winding speed, that is to say one revolution of the core of the barrel for each one-fourth of an hour, while the portion of this curve situated at the right of the line 12 indicates the slipping moment for a rapid winding speed, that is to say 9 revolutions of the core of the barrel per minute.

The observation of this curve permits to ascertain on the one hand that the difference between the slipping moments maximum and minimum (Mgl., and Mgl., is relatively important, especially for the slow winding, and that this difference is not the same in the two areas of the curve, that signifies that the wind speed has an effect in the winding condition of the main spring, that, obviously, is an inconvenience, since the wind of the spring, when it is entirely wound and when the self winding of the device of the watch continues to operate, should not vary with the speed at which the winding is effected.

Moreover, it can be seen that there is a strong difference between the average value of Mgl. (Mgl.,,,,,,, and M that signifies that, when the self-winding device of the watch operates while the main spring is already entirely wound, an overwind is produced.

The diagram of HO. 4, the upper curve of which indicates also the slipping moment of the blade of the spring, at the left of the vertical line 13 of this figure, for a low winding of one revolution for one-fourth of an hour, and at the right of this line for a rapid winding of 9 revolutions per minute, shows that the differences between the slipping moment maximum (Mgl., and the slipping moment minimum (Mgl.,,,,,,) are much lower than in the case of FIG. 3, and substantially the same in the two portions of the curve, that signifies that the slipping is unsensible to the differences of the winding speed. On the other hand, the average slipping moment (Mgl.,,,,,,, is much closer to the maximum moment M of the main spring at the moment where the unwinding thereof starts, that signifies that the self-winding device can operate permanently without producing a substantial overwind ofthe main spring.

One ascertains moreover, while comparing FIGS. 3 and 4, that the diagrams of the moments of forces of the main springs considered are not identical, this of FIG. 4 being better than this one of Flg. 3.

It is an indirect consequence of the present arrangement due to the gain of room, in the barrel, which is produced thereby. This gain of room permits to increase substantially the number of the revolutions developed by the main spring whereby an amelioration of the average efficiency of the spring and of its diagram are obtained.

It is to be noted that there are many parameters, in the present arrangement, which can vary, especially in function of the type of clockwork on which the present driving device is used.

Thus, the entrance portion 2b of the terminal blade of the main spring can extend on a sector, measured at the center of the barrel, being able to vary from 40 to 180 for instance. it is the same for the decreasing portion 2d of this blade. The terstead of bearing on the outer portion 2a.

So far as this terminal portion 22, separated of the wall 1 of the barrel, is concerned, it could extend on a sector going from 20 to for instance.

The maximum thickness of the terminal blade of the main spring will vary, also according to the type of the clockwork, from 1,2 to 3 times the nominal thickness of the blade.

What I claim is:

1. Main spring and barrel driving device for timepiece, characterized by the terminal blade of the main spring being made of one piece integral with the main spring and comprising at least two portions, one of which, called the entrance portion, has, at its beginning, a thickness equal to the thickness of the blade of the main spring and which increases in thickness in the direction of the outer extremity of said blade, and the other portion of which, called the output portion, has, at its beginning, a thickness equal to the greatest thickness of the end of the first portion and which decreases in thickness in the direction of the extremity of the said blade, the arrangement being such that theextremity of the output portion of the blade does not bear continuously on the inner face of the wall of the barrel but bears on this wall at two points situated at a distance one from another, one of which is constituted by the proper extremity of this portion, the spring bearing on said proper extremity for exerting thereon a pres sure varying with its wind in such a way that, when the said wind increases, the said pressure decreases, thus permitting the said blade to rotate in the barrel when the wind of the main spring reaches a critical value, this rotation releasing the said wind so that the pressure exerted on the output portion of the blade increases such that the said blade becomes rigid with the barrel.

2. Driving device as claimed in claim 1, characterized by the fact that the thickness of the free extremity of the output por tion of the tenninal blade of the main spring corresponds to the nominal thickness of its blade.

3. Driving device as claimed in claim 1, characterized by the fact that the terminal blade of the main spring comprises a third portion, situated between the entrance and the output portions, the .thickness of which, which is constant, corresponds to the maximum thickness of the terminal blade, that is to say to the thickness of the extremity of the entrance portion and to the thickness of the beginning of the output portion.

4. Driving device as claimed in claim 1, characterized by the fact that the terminal portion of the output portion of the terminal blade of the main spring, distant from the wall of the barrel, extends on a sector, measured at the center of the barrel, going from 20 to 120.

5. Driving device as claimed in claim 1, characterized by the fact that the maximum thickness of the terminal blade of the main spring is of l, 2 to 3 times the nominal thickness of its blade.

6. Driving device as claimed in claim 1, characterized by the fact that the entrance and the output portions of the terminal blade of the main spring extend each on a sector, measured at the center of the barrel, going from 40 to 7. Driving device as claimed in claim 6, characterized by the fact that the intermediary portion of the terminal blade of the main spring extends on a sector, measured at the center of the barrel, which does not exceed 280. 

1. Main spring and barrel driving device for timepiece, characterized by the terminal blade of the main spring being made of one piece integral with the main spring and comprising at least two portions, one of which, called the entrance portion, has, at its beginning, a thickness equal to the thickness of the blade of the main spring and which increases in thickness in the direction of the outer extremity of said blade, and the other portion of which, called the output portion, has, at its beginning, a thickness equal to the greatest thickness of the end of the first portion and which decreases in thickness in the direction of the extremity of the said blade, the arrangement being such that the extremity of the output portion of the blade does not bear continuously on the inner face of the wall of the barrel but bears on this wall at two points situated at a distance one from another, one of which is constituted by the proper extremity of this portion, the spring bearing on said proper extremity for exerting thereon a pressure varying with its wind in such a way that, when the said wind increases, the said pressure decreases, thus permitting the said blade to rotate in the barrel when the wind of the main spring reaches a critical value, this rotation releasing the said wind so that the pressure exerted on the output portion of the blade increases such that the said blade becomes rigid with the barrel.
 2. Driving device as claimed in claim 1, characterized by the fact that the thickness of the free extremity of the output portion of the terminal blade of the main sprIng corresponds to the nominal thickness of its blade.
 3. Driving device as claimed in claim 1, characterized by the fact that the terminal blade of the main spring comprises a third portion, situated between the entrance and the output portions, the thickness of which, which is constant, corresponds to the maximum thickness of the terminal blade, that is to say to the thickness of the extremity of the entrance portion and to the thickness of the beginning of the output portion.
 4. Driving device as claimed in claim 1, characterized by the fact that the terminal portion of the output portion of the terminal blade of the main spring, distant from the wall of the barrel, extends on a sector, measured at the center of the barrel, going from 20* to 120*.
 5. Driving device as claimed in claim 1, characterized by the fact that the maximum thickness of the terminal blade of the main spring is of 1, 2 to 3 times the nominal thickness of its blade.
 6. Driving device as claimed in claim 1, characterized by the fact that the entrance and the output portions of the terminal blade of the main spring extend each on a sector, measured at the center of the barrel, going from 40* to 180*.
 7. Driving device as claimed in claim 6, characterized by the fact that the intermediary portion of the terminal blade of the main spring extends on a sector, measured at the center of the barrel, which does not exceed 280*. 